Comprehensive Survey of Seismic Hazard at Geothermal Sites by a Meta-Analysis of the Underground Feedback Activation Parameter a fb

Arnaud Mignan, Marco Broccardo and Ziqi Wang
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Arnaud Mignan: Institute of Risk Analysis, Prediction and Management (Risks-X), Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China
Marco Broccardo: Department of Civil, Environmental and Mechanical Engineering, University of Trento, 38123 Trento, Italy
Ziqi Wang: Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720, USA

Energies, 2021, vol. 14, issue 23, 1-15

Abstract: Global efforts to tame CO 2 emissions include the use of renewable energy sources, such as geo-energy harnessing. However, injecting pressurised fluids into the deep underground can induce earthquakes, hence converting CO 2 -related risk into seismic risk. Induced seismicity hazard is characterised by the overall seismic activity a f b that is normalised by the injected fluid volume V and the parameter b of the Gutenberg–Richter law. The ( a fb ,b ) set has so far been estimated for a dozen of reservoir stimulations, while at least 53 geothermal fluid stimulations are known to exist, based on our survey. Here, we mined the induced seismicity literature and were able to increase the number of estimates to 39 after calculating a fb from related published parameters and by imputing b with its expectation where this parameter was missing (0.65 ≤ b ≤ 2.9, with mean 1.16). Our approach was a two-step procedure: we first reviewed the entire literature to identify seismic hazard information gaps and then did a meta-analysis to fill those gaps. We find that the mean and median a fb estimates slightly decrease from a fb ≈ −2.2 to a fb = −2.9 and −2.4, respectively, and that the range of observations expands from −4.2 ≤ a fb ≤ 0.4 to −8.9 ≤ a fb ≤ 0.4, based on a comprehensive review unbiased towards high-seismicity experiments. Correcting for potential ambiguities in published parameters could further expand the range of possibilities but keep the mean and the median relatively close to original estimates, with a fb ≈ −2.3 and −2.4, respectively. In terms of the number of earthquakes induced (function of 10 a fb ), our meta-analysis suggests that it is about half the number that could previously be inferred from published a fb estimates (i.e., half the seismic hazard). These results are hampered by high uncertainties, demonstrating the need to re-analyse past earthquake catalogues to remove any ambiguity and to systematically compute a fb in future geothermal projects to reduce uncertainty in induced seismicity hazard assessment. Such uncertainties are so far detrimental to the further development of the technology.

Keywords: seismic hazard; anthropogenic hazard; geo-energy; risk transfer; meta-analysis (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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